OPTIMIZATION OF A METAL WAVE-GUIDE CAVITY FOR A SUBMILLIMETER LASER

Theoretical and experimental investigations were made of the transvers e modes of a submillimetre laser with a cavity in the form of an overs ize circular metal waveguide. It was found that, for uniform and nonun iform reflectors, the mode formed by the lowest TE0m guided waves had the highest output power and could be selected by a suitable choice of the length of the free-space distance between the waveguide and a ref lector, A study was made of the increase in the power and in the degre e of polarisation of the output radiation when the outcoupling apertur e was displaced from the cavity axis, The experimental results agreed with a numerical calculation carried out in accordance with the propos ed procedure.